Bedsores are attributed to bad circulation of the blood in those parts of the body which press hardest against the mattress of the bed since the patient's weight is not evenly supported by his body. Attempts have therefore been made to produce beds such that the pressure of the mattress is exerted over the greatest possible area of the body and is at all points less than a threshold value which corresponds substantially to the lymph flow pressure.
It has also been observed that the muscles of the body are more completely relaxed when the body is immersed in a liquid. Therefore a bed has been proposed which comprises a tank which is partially filled with a liquid, for example water, the patient being separated from the liquid by a water-tight cloth cover which is sufficiently flexible to take up the shape of his body. "Water beds" of this kind have several disadvantages. Firstly, it should remembered that an adult floats in water in the lying position when the greater part of the body is sunk below the surface of the water. In a water bed, in which an attempt is made to reproduce the preceding conditions, it is clear that the patient will have the disagreable impression of being trapped in the cover which surrounds him. Further, air cannot flow freely between the patient and the cover which results in difficulties concerned firstly with the provision of sterile surroundings and secondly with easy heating of the patient.
Preferred embodiments of the present invention avoid these disadvantages.